The chassis of electronic devices such as personal computers and servers are made of metal or plastic. In recent years, due to increased awareness of environmental load and ecology, the development of so-called green products, which are low in environmental load and therefore ecological, have been drawing attention.
For this reason, metallic materials, which are easier to recycle than plastics, have been used for the chassis of electronic devices. As for the metals used for the chassis of electronic devices, iron, steel, stainless steel, aluminum, magnesium, and the like are available, for example. Among them, galvanized steel sheets obtained by galvanizing an iron surface have been used widely.
In a case of using metal for the chassis of electronic devices, coating is usually applied to the metal to prevent rust and improve the quality of appearance (visual appeal) and durability. Currently, organic coating using organic solvents are predominating the coating of the chassis of electronic devices.
However, the organic solvents contain volatile organic compounds (hereinafter, referred to as “VOCs”), which are a cause of air pollution. The organic solvents may be vaporized and released to the atmosphere during the coating. Moreover, during bake drying, the organic solvents may be decomposed into carbon dioxide and water, and the carbon dioxide, which is regarded as a cause of the global warming, may be released to the environment.
Powder coating has been known as a coating method using no organic solvent. In powder coating, a voltage is applied between an electrostatic gun configured to spray a coating powder and a coating object, and the electrically charged powder is adhered to the coating object. Then, the coating object is subjected to a heat treatment (bake drying) at a predetermined temperature to planarize the surface of the coating film.
Patent Document 1: Japanese Laid-open Patent Publication No. 2008-179803
Patent Document 2: Japanese Laid-open Patent Publication No. 2003-49120
Patent Document 3: Japanese Laid-open Patent Publication No. 09-276791